Sealing and testing segmented tools

ABSTRACT

A substantially air-tight triple seal arrangement along a seam between first and second tool segments comprises inner, middle and outer seals forming first and second substantially air tight vacuum chambers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional U.S. PatentApplication No. 61/829,639 filed May 31, 2013, which is incorporated byreference herein.

BACKGROUND INFORMATION

1. Field

The present disclosure generally relates to segmented tools havingmultiple pieces that are sealed together, and deals more particularlywith a triple seal arrangement and related method allowing the integrityof the individual seals to be tested and monitored.

2. Background

Some tools comprise multiple pieces or segments that must be assembled,but which are required to function and perform function as a seamless,single tool. For example, in the aircraft industry, a large compositefuselage section may be laid up on, vacuum bagged and then autoclavecured on a generally cylindrical mandrel comprising multiplecircumferential mandrel segments. The mandrel segments are assembledalong seams. Following curing and de-bagging, the mandrel segments mustbe disassembled in order to allow release and removal of the curedfuselage section from the tool.

Each seam between the mandrel segments may be sealed with asubstantially air-tight seal extending along joining surfaces ofadjacent mandrel segments. Air leakage through any of one of these sealsmay reduce compaction pressure applied to the fuselage section duringcuring. A reduction in compaction pressure during curing due to an airleak may have an undesirable effect on the quality and/or performance ofthe cured fuselage section.

One proposed solution to the problem of seal leakage involves theprovision of double seals along the seams between the mandrel segmentseams. The double seals are arranged to form a chamber that may be usedto perform a pass or fail leak test, however, the test does not indicatewhich of the double seals may have lost its integrity. If the testfails, indicating that the integrity of at least one of the seals mayhave been compromised, the tool segments must be disassembled, and theseals must be repaired or replaced, following which the mandrel segmentsmust be reassembled and the leak test must be repeated. The process ofdisassembling/reassembling and replacing the seals is time consuming,labor intensive and may reduce production throughput and build rate.

Accordingly, there is a need for a method of sealing and testing theintegrity of seals in segmented tools such as mandrels that allowscontinuous monitoring of seal integrity. There is also a need for a sealarrangement and testing method which will identify which, if any, of theseals are leaking and whether at least one seal has retained itsintegrity.

SUMMARY

The disclosed embodiments provide a method and system for sealing andtesting multi-piece tools such as segmented mandrels, in an autoclaveenvironment. A triple seal along seams between the mandrel segmentsprovide added protection against loss vacuum pressure due to seal leaks.The triple seal may be tested for leaks during assembly of the mandrels,before a layup is placed on the tool and loaded into an autoclave. Theneed for replacing and/repairing seals is reduced, the quality of curedparts may be improved, and production throughput may be increased.

According to one disclosed embodiment, a method is provided for sealingand monitoring multiple segments of a mandrel in an autoclaveenvironment. The method includes forming an inner bag vacuum chamberoverlapping ends and seams of the mandrel segments and an inner sealbetween the mandrel segments, and forming an outer vacuum bag chamberand an H-shaped seal area on opposite ends of the inner bag vacuumchamber. The method also includes forming an outer seal chamber usingthe H-shaped seal area, the inner seal and a middle seal, forming aninner seal chamber using the middle seal and the inner seal, andmonitoring the integrity of any of the inner seal, the middle seal andthe outer seal. The method may further comprise pressing the inner seal,the middle seal, the outer seal and legs of the H-shaped seal area intogrooves within the mandrel segments. Forming the outer vacuum bagchamber includes sealing the legs of the H-shaped seal area to the innerand outer vacuum bags. Forming the outer bag vacuum chamber includessealing legs of the H-shaped seal area to the inner seal and the middleseal. Monitoring the integrity includes sensing a change in vacuumpressure within any of the inner bag vacuum chamber, the inner sealchamber and the outer seal chamber.

According to another embodiment, a method is provided of sealing andtesting the integrity of seals between at least two segments of a tool,comprising arranging an inner seal, an outer seal and a middle seal toform first and second seal chambers between the two tool segments, andapplying a vacuum to each of the first and second seal chambers. A leakin the inner seal or the outer seal is detected by sensing a change invacuum pressure within the first and second seal chambers. The methodmay further comprise placing an H-shaped seal area between the two toolsegments, and connecting legs of the H-shaped seal area to each of themiddle and the outer seals. The method may also comprise placing aninner vacuum bag over the two tool segments, and sealing the innervacuum bag to the H-shaped seal area. The method may further compriseplacing an outer vacuum bag over the two tool segments covering theinner vacuum bag, and sealing the outer vacuum bag to legs of theH-shaped seal area. The method may also comprise using the outer vacuumbag to apply pressure to a seal between the inner vacuum bag and theH-shaped seal area.

According to still another embodiment, a method is provided of autoclaveprocessing a composite part on a segmented tool, comprising forming atriple seal between adjoining segments of the tool, including forming aninner seal, a middle seal and an outer seal, placing an inner vacuum bagover the segmented tool covering the composite part, and forming aninner bag vacuum chamber by forming a seal between the inner vacuum bagand the inner seal. The method may also comprise placing an outer vacuumbag over the segmented tool covering the inner vacuum bag, forming anouter bag vacuum chamber by forming a seal between the outer vacuum bagand the outer seal, drawing vacuums respectively within the inner vacuumbag chamber and the outer vacuum bag chamber, and using the outer vacuumbag to apply pressure to the seal between the inner vacuum bag and theinner seal. The method further includes compressing the triple seal byapplying autoclave pressure to the segments of the tool. The method mayalso comprise detecting a leak in any one of the inner seal, the middleseal or the outer seal. The inner seal, the middle seal and the outerseal are arranged to form an inner seal chamber and an outer sealchamber, and detecting the leak is performed by sensing a change invacuum pressure in either the inner seal chamber or the outer sealchamber. Forming the outer vacuum bag chamber further includes formingan H-shaped seal between the adjoining segments of the tool outside ofthe inner vacuum bag chamber.

According to still another embodiment, a substantially air-tight sealarrangement along a seam between first and second tool segments isprovided, comprising inner, middle and outer seals forming first andsecond substantially air tight vacuum chambers. The inner, middle andouter seals extend along a length of the seam, and are arranged in anH-shaped pattern at each of opposite ends of the seam. The first andsecond tool segments are arranged to form a layup surface, and theH-shaped pattern includes first and second legs adapted to be sealed tofirst and second vacuum bags covering the layup surface. The inner, themiddle and the outer seals are spaced apart from, and extendlongitudinally along the seam. In one variation, the inner and middleseals are spaced apart from each other and form the first vacuumchamber, and the middle and outer seals are spaced apart from each otherand form the second vacuum chamber. The seal arrangement may furthercomprise an H-shaped seal area located at opposite ends of the seam andconnected to the middle seal and the outer seal. Each of the first andsecond vacuum chambers is adapted to be coupled with a vacuum source anda vent for independently testing the inner, middle and outer seals forair leaks. The seal arrangement may also comprise first and secondvacuum probes are respectively sensing vacuum pressure in the first andsecond vacuum chambers.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description of an illustrative embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is illustration of a perspective view of a segmented mandrelhaving seams with triple seals according to the disclosed method.

FIG. 2 is an illustration of a cross-sectional view of a composite shelllaid up and cured on the segmented mandrel shown in FIG. 1.

FIG. 3 is an illustration of a sectional view taken along the line 3-3in FIG. 1.

FIG. 4 is illustration of a perspective view of the forward end of thetriple seal between mandrel segments at the location along the seamdesignated as “4” in FIG. 1.

FIG. 5 is illustration of a perspective view of a middle section of thetriple seals between the mandrel segments at the location along the seamdesignated as “5” in FIG. 1.

FIG. 6 is illustration of a perspective view of an aft end of the tripleseals between the mandrel segments at the location along the seamdesignated as “6” in FIG. 1.

FIG. 7 is an illustration of a cross-sectional view of anotherembodiment of a seam between two of the mandrel segments.

FIG. 8 is an illustration of a cross-sectional view of a furtherembodiment of a seam between two of the mandrel segments.

FIG. 9 is illustration of a diagrammatic cross-sectional view along oneof the seams, showing how the triple seal is connected to the inner andouter vacuum bags.

FIG. 10 is an illustration similar to FIG. 9, but showing a temporaryplate having been installed for testing the triple seal during assemblyof the mandrel segments.

FIG. 11 is an illustration of a functional block diagram showing thecomponents of the segmented mandrel and a related control system fortesting and monitoring the triple seal.

FIG. 12 is an illustration of a flow diagram of a method of sealing asegmented tool.

FIG. 13 is an illustration of a flow diagram of an alternate embodimentof a method of sealing a segmented tool.

FIG. 14 is an illustration of a flow diagram of aircraft production andservice methodology.

FIG. 15 is an illustration of a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a segmented layup tool 20 (FIG. 1),sometimes also hereinafter referred to as a segmented mandrel 20, may beused as a mandrel on which a composite part may be laid up and cured.For example, and without limitation, the segmented mandrel 20 may beused to layup and a cure the composite shell 36 shown in FIG. 2. Thecomposite shell 36 includes an outer composite skin 38 stiffened bylongitudinally extending, composite stringers 40. Although not shown inFIG. 2, the composite shell 36 may be attached to a circumferentiallyextending, internal frame to form a barrel section of an airplanefuselage (not shown).

The layup tool 20 includes a forward end 26 and an aft end 28, andcomprises a plurality of mandrel segments 22 that are joined togetheralong longitudinal seams 24. As will be discussed below in more detail,the seams 24 include a triple, substantially air-tight seal (not shownin FIG. 1) that seals the mandrel segments together 22 so that they actas a single tool. In the illustrated embodiment, the layup tool 20 has agenerally tapered cylindrical or barrel shape, however other shapes arepossible, depending upon the shape of the part to be fabricated.

The mandrel segments 22 collectively form a layup surface 30 upon whichcomposite material such as pre-preg, may be laid up to form thecomposite shell 36 shown in FIG. 2. The layup surface 30 forms the IML(inner mold line) of the composite skin 38, and may include a pluralityof circumferentially spaced, longitudinally extending stringers grooves32 into which preformed composite stringer layups (not shown in FIG. 1)may be placed before the skin 38 is laid up over the layup surface 30.The layup tool 20 further includes a substantially smooth,circumferentially extending bands 34 on the forward and aft ends 26, 28which are located longitudinally beyond the layup surface 30. The bands34 provide a surface to which one or more later discussed vacuum bags(not shown in FIG. 1 or 2) may be attached and sealed in order tocompact and consolidate the composite shell 36 during curing, which maybe carried out within an autoclave (not shown).

FIGS. 3-6 illustrate one embodiment of a lap joint or seam 24 betweentwo adjacent ones the mandrel segments 22 a, 22 b. FIG. 3 depicts acomposite skin 56 having been laid up on layup surface 30, covered by acaul plate 58, an inner vacuum bag 60 and an outer vacuum bag 94. Forsimplicity of description, additional elements such as release films,breathers, etc. are not shown. As will be discussed later in moredetail, the inner vacuum bag 60 is sealed to the bands 34 (FIG. 1),outside of the layup surface 30. In one embodiment, the seams 24 betweenthe mandrel segments 22 a, 22 b are formed by overlapping, peripheralinner and outer flanges 68, 70 forming mating, sealing surfaces 42. Thesealing surfaces 42 are sealed together by a substantially air-tighttriple seal 44 comprising an outer first seal 46, a middle second seal48, and an inner third seal 50. The opposite ends of the seals 46, 48,50 are arranged and connected to form H-shaped seal areas 82 which arerespectively located beyond the ends of the of the skin layup 56,beneath the bands 34.

Referring to FIGS. 4 and 6, each of the H-shaped seal areas 82 comprisesa pair of inner legs 83, 84, a pair of outer legs 85, 86 and a cross leg87. In the illustrated embodiment, the legs 83, 84, 85, 86 and 87 arearranged in the shape of an “H”, however, depending upon theapplication, these legs may be arranged to form other shapes. The outerends or tips 85 a, 86 a of the outer legs 85, 86 are respectively sealedto the inner and outer vacuum bags 60, 94 (see FIG. 9). The seals 46,48, 50 may be formed, for example and without limitation, by castingand/or extruding a suitable material such as silicone. The outer, middleand the inner seals 46, 48, 50 respectively, are circumferentiallyspaced apart from each other, and in the illustrated embodiment, areheld within respectively associated grooves 52 (FIG. 3) formed in thesealing face 42 of the outer flange 70. The tips 85 a, 86 a may beformed of a material such as, without limitation, Viton® or a similarfluoroelastomer which is suited to provide good adherence to vacuum bagsealant (not shown) used to seal the tips 85 a, 85 b to the inner andouter vacuum bags 60, 94. In other embodiments, the outer, middle andthe inner seals 46, 48, 50 respectively, as well as the H-shaped sealareas 82 may be held in grooves (not shown) formed in the inner flange68, and seal against the outer flange 70. In still other embodimentssome of the seals 46, 48, 50 and the seal area 82 may be formed in eachof the inner and outer flanges 68, 70 respectively.

The area between the middle seal 48 and the inner seal 50 forms oninner, first seal chamber 64, and the area between the middle seal 48and the outer seal 46 forms an outer, second seal chamber 66. The innerflange 68 is provided with at least one vacuum port 72 and a pressureprobe 76 which communicate with the outer seal chamber 66. The innerflange 68 is also provided with at least one vacuum port 74 and apressure probe 78 which communicate with the inner seal chamber 64. Thevacuum port 72 is used to selectively draw a vacuum or vent the outerseal chamber 66, and a change in the pressure within the outer sealchamber 66 may be sensed by pressure probe 76. Similarly, the vacuumport 74 is used to selectively draw a vacuum or vent the inner sealchamber 64, and a change in the pressure within the inner seal chamber64 may be sensed by the vacuum pressure probe 78. Although not shown inFIG. 3, one or more vacuum ports and pressure probes are coupled withthe area beneath each of the inner and outer vacuum bags 60, 94 in orderto evacuate the vacuum bag 60, 94 and separately sense vacuum pressureswithin the inner and outer vacuum bags 60, 94. The inner bag 60 forms aninner bag vacuum chamber 92 (FIG. 9) within which a part vacuum 71 isdrawn. The compaction pressure applied by the inner bag 60 to thecomposite skin layup 56 is supplemented by pressure applied by the outerbag 94, and external autoclave pressure 62.

FIG. 7 illustrates an alternate embodiment of one of the seams 24employing a triple seal 44, similar to the embodiment shown in FIG. 3.In this example, the seams 24 between adjacent mandrel segments 22 a, 22b are formed adjacent to the centerline 54 of the stringer grooves 32into which stringer layups (not shown) are placed before the compositeskin 38 is laid up over the layup tool 20. In this example, part of eachstringer groove 32 is formed along each of the mandrel segments 22 a, 22b at the seam 24.

FIG. 8 illustrates a further embodiment of a seam 24 between adjacentmandrel segments 22 a, 22 b. In this example, the mandrel segments 22 a,22 b respectively have opposing flanges 88, 90 which extend radiallyinwardly from the layup surface 30, effectively forming a sealed jointbetween the mandrel segments 22 a, 22 b along the seam 24.

Attention is now directed to FIG. 9 which diagrammatically illustratescomponents of the layup tool 20 along one of the seams 24; a caul plate,breathers, and release films having been omitted for simplicity. Thecomposite skin 56 is laid up on the layup surface 30 which forms the IMLof the finished part. The inner vacuum bag 60 is sealed by an inner bagseal 100 to the layup tool 20 around the band 34, and to the tips 85 aof the outer legs 86 of the H-shaped seal area 82. In embodimentsutilizing a caul plate (not shown), the inner vacuum bag 60 may besealed to the caul plate or to a caul plate vacuum bag (not shown).

The outer vacuum bag 94 is sealed by an outer bag seal 98 to the bands34, outside of the inner bag seal 100, and to the tips 86 a of the outerlegs 85 of the H-shaped seal area 82. The outer seal legs 85, 86 alongwith seal legs 87 form an outer bag vacuum chamber 96 which communicateswith the area 93 beneath the outer vacuum bag 94. The inner vacuum bag60 is in communication with an inner vacuum bag chamber 92 formed by theinner seal 50 and the outer legs 86 of the H-shaped seal area 82. Theinner seal chamber 64 is defined by the middle seal 48, the inner seal50 and the inner legs 83, 84 of the H-shaped seal area 82. The outerseal chamber 66 is defined by the outer seal 46, the middle seal 48 andthe inner legs 83, 84 of the H-shaped seal area 82. During processing ofthe composite skin layup 56 in an autoclave, evacuation of the outervacuum bag 94 draws the outer vacuum bag 94 down against and compressesthe inner bag seal 100. The compressive force applied to the inner bagseal 100 by the outer vacuum bag 94 supplements the applied autoclavepressure 62, to reduce the possibility of air leaks through the innerbag seal 100.

The area 80 beneath the inner vacuum bag 60 along with the inner bagvacuum chamber 92 are coupled with a vacuum ports 104. One or morevacuum pressure probes 106 are provided to sense a change in vacuumpressure within the inner vacuum bag 60 and the inner bag vacuum chamber92. Similarly, one or more vacuum ports 74 are coupled with the innerseal chamber 64 to selectively draw a vacuum or vent the inner sealchamber 64. One or more vacuum pressure probes 78 are used to sense achange in vacuum pressure within the inner seal chamber 64. Also, one ormore vacuum ports 72 are coupled with the outer seal chamber 66 toselectively draw a vacuum or vent the outer seal chamber 66. One or morepressure probes 76 are used to sense a change in vacuum pressure withinthe outer seal chamber 66. Additional vacuum ports 102 are used toselectively draw a vacuum in, or vent the outer bag vacuum chambers 96.

Referring now to FIG. 10, correct assembly of the mandrel segments 22shown in FIG. 1, and the integrity of triple seal 44 as well as theH-shaped seal area 82 may be tested as the mandrel segments 22 are beingassembled, prior to placing a composite layup on the layup tool 20 forprocessing. By testing the triple seal 44 during the mandrel assemblyphase, seal leaks may be detected and corrected before the tool 20 andcomposite layup is loaded into an autoclave. In order to test the tripleseal 44, a temporary test plate 105 is placed over each seam 24 betweenthe mandrel segments 22, and is sealed to the tips 85 a, 86 a of theH-shaped seal area 82 by outer seal 98 and inner seal 100. The testplate closes off the inner bag vacuum chamber 92 and the outer bagvacuum chamber 96. Vacuums are drawn in the inner seal chamber 64, theouter seal chamber 66, the inner bag vacuum chamber 92, and the outerbag vacuum chamber 96. A leak in the outer seal 46, the middle seal 48or inner seal 50 results in a change in vacuum pressure within the innerseal chamber 64, the outer seal chamber 66 and/or the inner bag vacuumchamber 92, and these changes in the vacuum pressure are detected by therespectively associated vacuum probes 78, 76 at 106.

Similarly, the integrity of the H-shaped seal area 82 may be checked forleaks. In the event that the outer legs 85 have a leak, the resultingchange in the vacuum pressure in the outer bag vacuum chamber 96 will bedetected by the vacuum probes 107. In the event that both of the outerlegs 85, 87 have a leak, the vacuum pressure within the inner bagchamber 92 is reduced, and this reduction in vacuum pressure is sensedby vacuum probes 106.

FIG. 11 broadly illustrates the components of a system for testing andmonitoring the integrity of seals used to seal a multi-piece, segmentedtool such as a segmented layup mandrel 20. A composite layup 56 may belaid up on the segmented mandrel 20, and covered by one or more vacuumbags 60, 94. The vacuum bags 60, 94 are individually sealed to thesegmented mandrel 20. The segments 22 of the mandrel 20 are sealed toeach other along seams 24 by a triple seal 44. The airtight chambers 64,66, 92 formed by the triple seal 44 are coupled with vacuum pressureprobes 76, 78, 106 and vacuum ports 72, 74, 102, 104, as previouslydescribed. A controller 108, which may comprise a programmed generalpurpose computer or a PLC (programmable logic controller) receivespressure data from the vacuum pressure probes 76, 78, 106 andselectively connects the vacuum ports 72, 74, 102, 104 with a vacuumsource 110 or a vent 115.

Referring now again to FIG. 9, after the mandrel segments 22 have beenassembled, and a composite skin 56 has been laid up on the layup surface30 of the mandrel 20, the mandrel 20 is placed in an autoclave (notshown) where autoclave pressure 62 and heat are applied. Vacuum ports72, 74, 102, 104 are used to draw vacuums the inner seal chamber 64, theouter seal chamber 66, the inner vacuum bag chamber 92 and the outer bagvacuum chamber 96. The vacuum generated within the inner bag vacuumchamber 92, along with autoclave pressure 62 compact and consolidate thecomposite layup 56 during a cure cycle. The outer vacuum bag 94 may addadditional compaction pressure to the composite skin layup 56, and alsoapplies a compressive force to the inner bag seal 100.

If the triple seal 44 is functioning properly (without air leaks),vacuum pressure probes 76, 78 and 106 register relatively low,preselected levels of vacuum pressure indicating that the integrity ofthe outer seal 46, the middle seal 48 and the inner seal 50 is intact.In the event of a leak in the outer seal 46, air pressure enters theouter seal chamber 66, causing a change (reduction) in the vacuumpressure within the outer seal chamber 66. This change in vacuumpressure is detected by the vacuum probe 76. In the event of a leak inthe outer seal 46, the middle seal 48 and the inner seal 50 maintain therequired vacuum pressure in the inner bag vacuum chamber 92.

In the event that both of the outer seal 46 and the middle seal 48 haveleaks, air pressure enters the inner seal chamber 64 but the inner seal50 maintains the required vacuum pressure in the inner bag chamber 92.Under these circumstances, the leak in the middle seal 48 allows airpressure to enter the inner seal chamber 64. A reduction in the vacuumpressure within the inner seal chamber 64 is detected by the vacuumpressure probe 78. In the event of leaks in each of the outer seal 46,middle seal 48 and inner seal 50, air pressure enters the inner vacuumbag chamber 92 and the resulting change in vacuum pressure is detectedby the vacuum probes 106.

It may be possible to detect a leak in the middle seal 48 undercircumstances where there is no leak in the outer seal 46. This middleseal 48 leak detection may be achieved by maintaining the vacuumpressure in the inner seal chamber 64 at a level that is greater thanthe vacuum pressure maintained in the outer seal chamber 66. Using thistechnique, a leak in the middle seal 48 will result in a change in thevacuum pressure which is detected by the vacuum pressure probes 78 inthe inner seal chamber 64.

The use of the outer bag 94 in combination with the H-shaped seal area82 provides further protection against loss of compaction pressure inthe event of seal leaks. The H-shaped seal area 82 along with the innerand outer bag seal 98, 100 form double seals with the outer bag 94 thatare independent of the outer seal 46, middle seal 48 and inner seal 50.Thus, in the event a loss of vacuum pressure within the bag vacuumchamber 92, the vacuum pressure is nevertheless maintained within theouter bag vacuum chamber 96 and within the area 93 beneath the outervacuum bag 94. Consequently, the outer vacuum bag 94 maintains therequired compaction pressure against the composite skin layup 56.

FIG. 12 illustrates the overall steps of a method of sealing and testingmultiple segments of a mandrel in an autoclave environment. At step 112,an inner bag vacuum chamber 92 is formed that overlaps the seams 24 ofthe mandrel segments 22 and an inner seal 50 between the mandrelsegments 22. At 114, an outer vacuum bag chamber 96 and H-shaped sealarea 82 are formed on opposite ends of the inner bag vacuum chamber 92.At 116, an outer seal chamber 66 is formed using the H-shaped seal area82, an outer seal 46 and a middle seal 48. At 118, an inner seal chamber64 is formed using the middle seal 48 and the inner seal 50. At 120, aleak in any one of the inner seal 50, the middle seal 48 or outer seal46 is detected. The leak may be affected by sensing a change in vacuumpressure within the inner and outer vacuum bag chambers 92, 96.

FIG. 13 illustrates the overall steps of an alternate method of sealingand testing the integrity of seals between at least two tool segments22. At step 122, an inner seal 50, an outer seal 46 and a middle seal 48are arranged to form first and second seal chambers, 64, 66respectively. At 124, a vacuum is applied to each of the first andsecond seal chambers 64, 66. At 126, a leak is detected any one of theinner seal 50, the outer seal 46 and an middle seal 48 by sensing achange in vacuum pressure within either of the first and second sealchambers 64, 66.

Embodiments of the disclosure may find use in a variety of potentialapplications, particularly in the transportation industry, including forexample, aerospace, marine, automotive applications and otherapplication where it is necessary to seal segmented tools, such as thoseused to autoclave process composite parts. Thus, referring now to FIGS.14 and 15, embodiments of the disclosure may be used in the context ofan aircraft manufacturing and service method 128 as shown in FIG. 14 andan aircraft 130 as shown in FIG. 15. Aircraft applications of thedisclosed embodiments may include, for example, without limitation,composite shells forming part of barrel-shaped fuselage sections. Duringpre-production, exemplary method 128 may include specification anddesign 132 of the aircraft 130 and material procurement 134. Duringproduction, component and subassembly manufacturing 136 and systemintegration 138 of the aircraft 130 takes place. Thereafter, theaircraft 130 may go through certification and delivery 140 in order tobe placed in service 142. While in service by a customer, the aircraft130 is scheduled for routine maintenance and service 144, which may alsoinclude modification, reconfiguration, refurbishment, and so on.

Each of the processes of method 128 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 15, the aircraft 130 produced by exemplary method 128may include an airframe 146 with a plurality of systems 148 and aninterior 150. Examples of high-level systems 148 include one or more ofa propulsion system 152, an electrical system 154, a hydraulic system156 and an environmental system 158. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the marine andautomotive industries.

Systems and methods embodied herein may be employed during any one ormore of the stages of the production and service method 128. Forexample, components or subassemblies corresponding to production process136 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 130 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 136 and 138, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 130. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft130 is in service, for example and without limitation, to maintenanceand service 142.

As used herein, the phrase “at least one of”, when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used and only one of each item in the list may be needed. Forexample, “at least one of item A, item B, and item C” may include,without limitation, item A, item A and item B, or item B. This examplealso may include item A, item B, and item C or item B and item C. Theitem may be a particular object, thing, or a category. In other words,at least one of means any combination items and number of items may beused from the list but not all of the items in the list are required.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different advantages as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A method for sealing and monitoring multiplesegments of a mandrel in an autoclave environment, comprising: formingan inner bag vacuum chamber overlapping ends and seams of the mandrelsegments and an inner seal between the mandrel segments; forming anouter vacuum bag chamber and an H-shaped seal area on opposite ends ofthe inner bag vacuum chamber; forming an outer seal chamber using theH-shaped seal area, an outer seal and a middle seal; forming an innerseal chamber using the middle seal and the inner seal; applyingautoclave pressure to the segments of the mandrel; and monitoring theintegrity of any of the inner seal, the middle seal and the outer seal.2. The method of claim 1, further comprising: pressing the inner seal,the middle seal, the outer seal and legs of the H-shaped seal area intogrooves within the mandrel segments.
 3. The method of claim 1, whereinforming the outer vacuum bag chamber includes sealing the legs of theH-shaped seal area to the inner and outer vacuum bags.
 4. The method ofclaim 1, wherein forming the outer bag vacuum chamber includes sealinglegs of the H-shaped seal area to the inner seal and the middle seal. 5.The method of claim 1, wherein monitoring the integrity includes sensinga change in vacuum pressure within any of the inner bag vacuum chamber,the inner seal chamber and the outer seal chamber.